The processing of semiconductor substrates is integral to the manufacture of integrated circuits. Most commonly, these substrates are in the form of silicon wafers that are exposed to a number of sequential processing steps including, but not limited to, chemical vapor deposition (CVD), physical vapor deposition (PVD), etching, planarization, and ion implantation.
The use of robotic cluster tools has become standard in semiconductor processing. Such tools can process a large number of substrates through many different processing technologies, and can perform repetitive tasks quickly and accurately. Most modern semiconductor processing systems include robotic cluster tools that integrate a number of process chambers together in order to perform several sequential processing steps without removing the substrate from the highly controlled processing environment. These chambers may include, for example, degas chambers, substrate pre-conditioning chambers, cooldown chambers, transfer chambers, chemical vapor deposition chambers, physical vapor deposition chambers, and etch chambers. The combination of chambers in a cluster tool, as well as the operating conditions and parameters under which those chambers are run, may be selected to fabricate specific structures using a specific process recipe and process flow.
Once the cluster tool has been set up with a desired set of chambers and auxiliary equipment for performing certain process steps, the cluster tool will typically process a large number of substrates by continuously passing them, one by one, through the chambers or process steps. The process recipes and sequences will typically be programmed into a microprocessor controller that will direct, control and monitor the processing of each substrate through the cluster tool. Once an entire cassette of wafers has been successfully processed through the cluster tool, the cassette may be passed to yet another cluster tool or stand alone tool, such as a chemical mechanical polisher, for further processing.
As the demand for wafer throughput in semiconductor fabrication lines has increased over time, the operating speeds of the robotic arms utilized in cluster tools has also had to increase. The attendant increase in momentum of the wafers as they move through the fabrication line has thus required that certain measures be taken to ensure and maintain the proper placement of wafers on the end effectors of the robotic arms.
Initially, this was achieved by providing recesses or walls on the end effecter blade that restricted the movement of the wafer during transfer from one processing chamber or tool to another. However, this approach was found to be unsatisfactory, because movement of the wafer on the end effecter blade was not always eliminated, and removal of the wafer from the end effecter blade became more challenging. Also, contact between the wafer and the surfaces of the end effecter blade frequently resulted in the introduction of metal contaminants into the wafer. The use of vacuum suction devices in the end effecter blade to maintain the wafer in position has also been utilized, but this approach is undesirable in that it significantly increases the complexity and cost of maintaining the tool.
More recently, end effecters have been developed which utilize elastomeric support pads to maintain the wafer in its proper position on the end effecter blade. An example of such an end effecter is illustrated in FIG. 1. The end effecter 101 depicted therein includes a blade 103 which is releasably mounted in a blade mount 105 by a plurality of set screws 107. The blade 103 is equipped with 5 mushroom-shaped elastomeric support pads 109, each adapted to grip the substrate sufficiently (e.g., by creating a sufficiently high coefficient of friction with respect to the surface of the substrate) to hold the substrate in place during processing. The support pads 109 are disposed upon a major surface of the blade 103 in a configuration which is adapted to support a wafer 111 in a first position removed from the blade mount 105, as shown in FIG. 2, and in a second position adjacent to the blade mount 105, as shown in FIG. 3. The first position, in which the wafer 111 is supported on the front three support pads 109, is the position most commonly used when the wafer 111 is being handled under atmospheric conditions, while the second position, in which the wafer 111 is supported on the back three support pads 109, is the position most commonly used when the wafer 111 is being handled under vacuum conditions.
End effectors of the type depicted in FIGS. 1-3 represent a significant improvement in the art, insofar as they allow wafers to be processed by cluster tools at very fast rates, with minimal movement of the wafer during transit. However, in practice, it has been found that the mushroom-shaped elastomeric support pads 109 utilized in these end effectors require frequent replacement and servicing.
There is thus a need in the art for an improved end effecter that overcomes the aforementioned infirmities. In particular, there is a need in the art for an end effecter with a more robust support pad design. These and other needs are met by the devices and methodologies disclosed herein.